This invention relates to a rope-type elevator system and, more particularly, to a linear motor elevator system in which a linear motor is used for driving the elevator car.
FIG. 5 is a general schematic diagram of one example of a conventional linear motor elevator system disclosed in Japanese Patent Laid-Open No. 1-271381, FIG. 6 is a front view of a counter weight of the conventional linear motor elevator system illustrated in FIG. 5 and FIG. 7 is a plan view of a brake unit of the conventional linear motor elevator system illustrated in FIG. 5.
In FIGS. 5 to 7, the conventional elevator system comprises an elevator car 1 and a counter weight 4 connected by means of a rope 5 extending around sheaves 2 and 3. The details of the counter weight 4 are illustrated in FIGS. 6 and 7, in which the counter weight 4 is vertically movably supported within a hoistway defined by hoistway walls 6 by means of a pair of secondary conductors 7 of the linear induction motor. It is seen that the secondary conductors 7 are secured to the walls 6 through mounting brackets 8 so that they extend vertically at the opposite sides of the counter weight 4. The counter weight 4 includes a pair of primary windings 9 each of which constitutes a linear induction motor together with the respective secondary conductors 7. The counter weight 4 also includes a pair of brake units 10 each engageable with the respective secondary conductors 7. As best seen from FIG. 7, the brake unit 10 comprises a pair of brake arms 12 pivotable about a pin 11, brake shoes 13 attached to first ends of the brake arms 12, a compression spring 14 disposed between the second ends of the brake arms 12 and an electric magnet 17 including an iron core 15 and a coil 16 wound on the core 15 and disposed between the second ends of the brake arms 12.
When the primary windings 9 of the linear induction motors mounted on the counter weight 4 are energized, a thrust force is generated between the secondary conductors 7 and the primary windings 9 so that the counter weight 4 is driven by the thrust force along the secondary conductors 7. Since the counter weight 4 is connected to the elevator car 1 through the rope 5, the movement of the counter weight 4 is transmitted to elevator car 1 so that the latter is driven within the hoistway.
When the coil 16 of the electromagnet 17 is not energized, the spring force of the compression spring 14 causes the brake arms 12 to pivot about the pin 11 to sandwich the secondary conductor 7 between the brake shoes 13 under pressure, so that the brake unit 10 serves to maintain the counter weight 4 stand still. When the coil 16 of the electromagnet 17 is energized, the electromagnetic attractive force acting on the brake arms 12 overcomes the spring force 14 to move the brake shoes 13 away from the secondary conductor 7, whereby the brake unit 10 is released to allow the counter weight 4 to freely travel along the secondary conductor 7.
In the above-described conventional linear motor elevator, there are provided two sets of linear induction motors each including the secondary conductor 7 mounted on the opposite side walls 6 of the hoistway and the primary winding 9 associated with the respective secondary conductors 7. Therefore, the conventional linear motor elevator requires two secondary conductors 7 each on one side of the counter weight, significantly increasing the price of the linear motor elevator.
Also, since the brake unit 10 is disposed in association with the secondary conductor 7, the brake arm 12 must have a sufficiently large arm length W2 on the shoe side for accommodating a relatively large height dimension W1 of the secondary conductor 7 between two brake arms 12. Also, the brake arm 12 must be thick and rigid in order to accurately transmit the braking force from the compression spring 14 and the electromagnet 17. Therefore, the brake arms 12 and the entire brake unit 10 are large and heavy, expensive.